1. Field of the Invention
The present invention relates to a conductive resin composite material suitable for the production of conductive molded articles.
2. Description of the Prior Art
The recent development in electronics technology needs shielding for static charge and electromagnetic waves which is made from a conductive resin composite material composed of a synthetic resin or rubber and carbon particles or fibers, having light weight, high strength, high conductivity, and good moldability. Unfortunately, a conductive resin composite material incorporated with carbon particles such as carbon black has a disadvantage that it needs to contain a large amount of carbon particles if it is to have a low resistance. The carbon particles incorporated in large quantities greatly increase the viscosity of the resin composite material, which leads to poor moldability. An additional disadvantage of the carbon-containing resin composite material is that the structure of carbon black is broken by shear at the time of mixing or molding, which leads to the deviation of resistivity. On the other hand, a conductive resin composite material incorporated with carbon fibers formed from organic fibers such as polyacrylonitrile fibers by the carbonization and subsequent graphitization also has a disadvantage that it does not provide a desired conductivity because carbon fibers themselves are short of conductivity.
In order to overcome these disadvantages, there was proposed in Japanese Patent Laid-open No. 218661/1986 a resin composite material having a low resistance and good moldability, which is formed by incorporating plastics or rubber with carbon fibers 0.05 to 4 .mu.m in diameter, with an aspect ratio (length-to-diameter ratio) of 20 to 1000, and having a uniform thickness with very few branches. Such carbon fibers are produced by pyrolyzing a hydrocarbon introduced into a reaction zone together with a specific organometallic compound (and, if necessary, a carrier gas). The carbon fibers undergo heat treatment according to need. Even this resin composite material needs a large amount of carbon fiber if it is to have a low resistance. The incorporation of carbon fiber in large quantities adversely affects the formability. In addition, however large the quantity of carbon fiber may be, the resistivity achieved by it is of the order of 10.sup.-2 .OMEGA..cm at the lowest.